While there are many variations of the artillery piece and the organization containing it, the 155mm howitzer (6.2 inch), or close approximations such as the Russian 152mm, has become the de facto worldwide standard for medium artillery howitzers. Even Russia, whose standard had been 152mm, is now starting to make a 155mm, the 2S19M1 variant of their 2S19 MSTA-S.  There still may be some 105mm howitzers either in resource-poor militaries, or units that have extreme weight restrictions on their weapons, or in special applications such as the airborne howitzer in the AC-130. For some time, the Russians and Chinese deployed an 130mm gun that outranged all 105mm and some 155mm howitzers.
While the 8-inch/203mm howitzer was also extensively used, and was almost always the most accurate indirect fire weapon not using precision-guided munitions, surface-to-surface missiles or air-to-surface missiles had longer range, greater accuracy, and more payload. This caliber stayed on into the 1990s with major militaries; heavier howitzers were going out of service toward the end of the Second World War.
There are two major categories: lightweight towed 155mm howitzers, and self-propelled, usually lightly armored, 155mm howitzers. Some "towed" howitzers, such as the Swedish Bofors FH77 series, may have small engines that can shift them for short distances, or may integrate with a wheeled truck rather than the full-tracked vehicle associated with self-propelled artillery.
Constant efforts to make a 155mm howitzer that can be towed by a medium truck or lifted by a medium helicopter have led to using metals long considered too exotic for artillery. One of the most recent, developed by British BaE Systems as the Ultralightweight Field Howitzer, and manufactured in the U.S. as the M777, contains a substantial amount of titanium. It is replacing the M198 howitzer, which does not have as advanced an electronic fit.
The weight problem addressed by howitzers of this class includes the ammunition. While the older M712 Copperhead guided shell worked well, it was prohibitively expensive. The M777, however, will routinely fire the new Raytheon/Bofors XM982 Excalibur GPS/Inertial Navigation-guided extended-range 155mm projectiles using the Modular Artillery Charge Systems (MACS). With more accurate, longer-range shells, the total system weight goes down because fewer rounds of ammunition will be needed. Since the cost of electronics has been dropping, the newer shells are more cost-effective as well as lighter.
South Africa has a reputation for developing extremely good artillery pieces. In the Gulf War, there was considerable concern that the towed Iraqi G5 howitzers outranged the U.S. M109A5 version then in service. U.S. target acquisition and artillery fire control made up for the distance in range; the excellent Iraqi pieces could be devastating if fired at a predesignated target, but the Iraqis were not able to locate and engage moving targets.
The U.S. M109 howitzer series is used by many countries. The continuing trend of treating artillery not just as a single piece, but as a system, continues to apply: the howitzers have companion M992 Field Artillery Ammunition Supply Vehicles (FAASV) . A variant on the M992, the M992A2 Fire Direction Center Vehicle (FDCV), serves each howitzer platoon.
Russia's  152 mm 2S19 MSTA-S self propelled howitzer went into service in 1989. It also has a Krasnopol guided shell. This round has inertial mid-course guidance and semi-active laser homing. The projectile has a range of 3 to 20 km, and can hit a target by the first shot without registration. Krasnopol is designated by the 1D15 (1D22) laser designator and has a 1A35 shot synchronisation system.
- MSTA-S 2S19 152mm Self Propelled Howitzer, Russia, ArmyTechnology.com
- M777 155mm Ultralightweight Field Howitzer, United Kingdom, Army Technology.com
- M712 Copperhead, Federation of American Scientists
- M992A1 FAASV Field Artillery Ammunition Supply Vehicles, Federation of American Scientists
- "PzH 2000 155mm Self-Propelled Howitzer, Germany", ArmyTechnology.com